This application claims the priority of PCT International No. PCT/DE01/00203, filed Jan. 18, 2001, and German Patent Document 100 03 944.8 filed Jan. 29, 2000 the disclosures of which are expressly incorporated by reference herein.
The invention relates to a process for the control of an internal combustion engine, whereby the internal combustion engine is equipped with a device to change a valve timing. A change in the valve timing means in this connection that variables of the valve timing, such as valve lift or phase position, can be adjusted by means of well-known means.
In such devices a change in the valve timing takes place as a function of the different operating parameters of the internal combustion engine. Such an operating parameter can be, for example, the actual load of the internal combustion engine. One possibility of detecting such a load is to scan the position of a throttle flap of the internal combustion engine. In particular in devices to change the valve timing, in which the valve timing is not adjusted continuously, but in steps, a change in the load of the internal combustion engine results in a change in the valve timing, when a load threshold, determined for the change over between steps, is exceeded. If the load of the internal combustion engine changes often in the area of the load threshold, the result is frequent shift operations in the valve timing, and thus an increased wear and under some circumstances also an unsatisfactory operating performance of the internal combustion engine.
Proceeding from this state of the art, the object of the invention is to provide a process to control an internal combustion engine with variable valve timing, in which a change in the valve timing takes place only when it is necessary for the operation of the internal combustion engine.
The invention solves this problem and is based on the knowledge that a change in the load of the internal combustion engine takes place especially when there is a shift operation in the transmission, connected at the end of the internal combustion engine. Therefore, according to the present invention the transmission, connected at the end of the internal combustion engine, is monitored as to whether there is a shift operation in the transmission. If such a shift operation is recognized, a change in the valve timing is suppressed. With this process the number of changes in the valve timing is significantly reduced in an advantageous manner and thus the wear properties of the valve timing and optionally the operating behavior of the internal combustion engine are improved, as a result during a shift operation in the transmission the performance characteristics of the internal combustion engine are not additionally affected by a change in the valve timing.
Thus, to recognize a shift operation in a manual transmission, a clutch be monitored and in the case of an open clutch a shift operation included such a monitoring can be performed, for example, in a very simple manner by scanning a clutch switch on the clutch pedal. In particular for a manual transmission the change in the load of the internal combustion engine is especially high, because here for a shift operation the load of the internal combustion engine is reduced to zero. In the case of an automatic transmission a shift operation can be recognized because a controller of the automatic transmission sends a signal, when this controller triggers a shift operation. Such a signal can be especially easy to generate and passed on, when the controller of the automatic transmission is connected to a controller for the valve timing by way of a databus, for example a CAN bus.
A shift operation can be recognized totally independent of the design of the transmission, in that a wheel speed signal is related to a motor speed signal. Should this relation change, then a shift operation has taken place, or the force flow between the internal combustion engine and the wheels of the motor vehicle has been interrupted in a different manner. This process can be implemented in a very simple manner, because the wheel speed signals are already detected in all motor vehicles as the driving speed signal or for an antilock braking system.
Finally it can be provided that after a recognized shift operation a change in the valve timing be suppressed for a predetermined period of time (i.e. a dead time), which follows immediately, in order to prevent in this manner that a load adjustment after a shift operation result in a change in the valve timing.